TPU powder slush for interior parts

An aqueous dispersion polymerization process was used to obtain particles of desired shape and diameter. Click to enlarge

With a mind toward improving the recyclability of interior plastic parts such as instrument panels and door trim, researchers from Sanyo Chemical Industries Ltd. and Toyota Motor Corp. have developed a thermoplastic polyurethane (TPU) powder slush material as an alternative to polyvinyl chloride (PVC) powder slush. The material is now in use on the Lexus LS430, among other vehicles.

PVC resin has good qualities in terms of product appeal (e.g., grain quality, touch perception), durability (e.g., resistance to scratches, heat, light, chemicals), and safety (e.g., antifogging, flame resistance), and therefore is in wide use as a general-purpose material. However, it is difficult to recycle if used as part of a composite, according to the researchers.

The TPU material they developed can be used in powder slush molding, a process used to form skins. However, TPU generally has poor anti-alcohol performance, researchers concluded. This problem had to be overcome because the common cleaner solvent for interior parts usually contains some type of alcohol. Through the study of various TPU formulas, sufficient anti-alcohol performance was achieved by introducing aromatic polyol.

Properties relating to temperature extremes are important for airbag deployment performance and moldability of powder slush, the researchers noted, and that's where aromatic polyol came up short. In response, the researchers undertook additional study for various types and amounts of plasticizer. Benzoic ester produced the best balance between compatibility with urethane polymer and anti-fogging performance.

The researchers considered using a thermoplastic olefin (TPO) instead of a TPU, but found the latter superior in terms of melting properties, adhesion to urethane foam, scratch resistance, and light resistance.

They also considered using vacuum molding instead of powder slush molding but determined that the latter produced better quality parts. In vacuum molding, an extruded plastic sheet is heated, shaped in a mold under vacuum, then cooled and released from the mold. In powder slush molding, a mold heated to a high temperature and a box filled with resin powder are swing-rotated together so the powder melts and flows in the mold, then cools and hardens.

Processing being a key technology in the development of TPU powder, particle shape and diameter were optimized by polymerization in an aqueous dispersion process rather than the conventional powdering method of cryogenic grinding. The chosen processing method also proved better in terms of cost and degree of perfection in the production process.

- Patrick Ponticel

Interior sounds from Owens

A new approach to filling vehicle interiors with audio system sounds reflects the next generation of existing flat panel speaker technology from Owens Corning Automotive.

"It's really a fully integrated solution," said Michael Kuhn, Business Leader for Interior Acoustic Systems for Toledo, OH-based Owens Corning Automotive. "Customers won't see the speaker (grilles) as such anymore."

Conventional loudspeaker technology involves magnets and coils, which basically move a cone to transform electric impulses into sound waves. The new technology eliminates the traditional channels needed for sound distribution, and instead excites a panel (such as a door panel, instrument panel, and/or headliner) via vibration.

"To create sufficient sound quality, you need surface materials or substrates with certain properties," said Kuhn, noting that the panel essentially takes over the function of a loudspeaker membrane.

Owens provides design and material expertise as part of its partner collaborations. "There are several pieces of the technology that come together for this," said Andrew Hopkins, Acting General Manager, Owens.

The patented technology underscores a method of joining composite materials to provide an integrated speaker sound through interior panels. Vehicles using this technology are expected as early as 2005 MY.

According to Owens executives, use of the technology offers many benefits. "The value of this technology is (derived) from space savings and being able to package things differently," said Hopkins. Kuhn added that the new speaker-less technology also equates to mass reduction, cost savings, and better sound quality.

- Kami Buchholz

More interior resins from GE

GE's CYTRA resin offers a low-gloss appearance for this glove box door.

GE Plastics' portfolio of engineering styrenic alloys offers an attractive alternative to polypropylenes for unpainted automotive interior cladding and trim applications. Called CYTRA, the resins give a more uniform, low-gloss appearance with all the benefits of a traditional engineering thermoplastic or polypropylene with the added performance of high impact resistance and dimensional stability over a wide temperature range, according to the company.

The product also offers good UV, scratch and mar, and chemical resistance (e.g., most aliphatic hydrocarbons, petrol, oils and greases, dilute acids and bases, detergents, cosmetics and body care products, and most aqueous salt solutions at ambient temperatures). A blend of acrylonitrile-butadiene-styrene and polybutyelene terephthalate using proprietary compatibilization technology, CYTRA gives a uniform, low-gloss appearance when molded with a fine-textured surface, the company says.

The resins represent a potential material cost savings of as much as 25% compared to traditional engineering thermoplastics and polypropylenes. They also fit within the acceptable range of low emissions and low odors set by the automotive industry for interiors.

GE is offering the resin in two alloy grades:

• CYTRA XCT 100 for applications such as instrument cluster bezel and cover, air nozzles and housings, defroster grilles, lower instrument panel center trim, and seat claddings.
• CYTRA XCT 200 for impact-sensitive areas such as air nozzles and housings, upper door trim, defroster grille, pillars, center console, and glove box.

GE also recently introduced six new Visualfx resin finishes based on an exclusive 2002 color and effects guide developed by fashion and aesthetics forecaster Agence de Style Peclers of Paris. The company used the SAE 2002 World Congress to launch Enyo, Lustre, Glass, Make-Up, Smoke, and Frost. Each correlating resin is formulated with the color and effect inherent in the pellet to create what GE calls "exceptionally rich-looking parts out of the mold without the need for what can often be costly secondary paint and coating operations."

Available in LEXAN polycarbonate resin, Enyo creates the appearance of tiny crystals and dramatic color changes. Lustre is available in pre-compounded LEXAN resin pellets and reproduces a pearl finish with a shiny, translucent base in soft pastel pinks and whites. Available in CYCOLAC acrylonitrile-butadiene-styrene (ABS) and LEXAN resins, Glass simulates the appearance of stained glass or gems with deep, transparent colors. Make-Up, available in CYCOLOY ABS/PC resin, involves rich color and subtle sparkles for a satiny appearance. Smoke effects include a translucent base with diffuser in a palette of grays and browns, while Frost effects produce subtle hues of pale, translucent color without sparkle or sheen; both are available in LEXAN resins.

- Patrick Ponticel